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<p>下面是JavaScript 1.8.1 的更新内容. 该版本已包含在 <a href="/en-US/Firefox/Releases/3.5">Firefox 3.5</a> 中.</p>
<p>JavaScript 1.8.1 是在语义上有适度更新的版本; 其主要更新是添加能够提升性能的<a class="new" href="/zh-CN/docs/SpiderMonkey/Internals/Tracing_JIT" rel="nofollow" title="SpiderMonkey/Internals/Tracing JIT">Tracemonkey即时编译器</a>。</p>
<h2 id="JavaScript_1.8.1_新特性">JavaScript 1.8.1 新特性</h2>
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<li><a href="/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object/getPrototypeOf"><code>Object.getPrototypeOf()</code></a></li>
<li><a href="/en-US/docs/Web/JavaScript/Guide/Using_native_JSON">原生支持 JSON</a></li>
<li><a href="/en-US/docs/Web/JavaScript/Reference/Global_Objects/String/Trim"><code>String.prototype.trim()</code></a></li>
<li><a href="/en-US/docs/Web/JavaScript/Reference/Global_Objects/String/TrimLeft"><code>String.prototype.trimLeft()</code></a></li>
<li><a href="/en-US/docs/Web/JavaScript/Reference/Global_Objects/String/TrimRight"><code>String.prototype.trimRight()</code></a></li>
<li><a href="/en-US/docs/Web/JavaScript/Reference/Global_Objects/String/startsWith"><code>String.prototype.startsWith()</code></a></li>
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<h2 id="JavaScript_1.8.1_功能更新">JavaScript 1.8.1 功能更新</h2>
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<li>对象和数组初始化器中的属性隐式设置不再在 JavaScript 中执行 setter。 这使得设置属性值的行为更具可预测性。</li>
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